The present invention relates to a semiconductor chip, a semiconductor device containing such semiconductor chips, a circuit substrate in which such a semiconductor device is incorporated, an electronic apparatus in which such a circuit substrate is mounted, and a method for producing them. Particularly, it relates to processing of through-holes for forming metal bumps.
The development of multimedia and information apparatuses has been remarkable in recent years. The data processing speed of electronic apparatuses has been improved with the advance of reduction in size and weight and increase in capacity. Micro-processors and memories have been improved in performance correspondingly remarkably. The technical progress of their peripheral equipment, however, has lagged relatively. For example, a CPU clock signal having a frequency over 300 MHz has a tendency to generate wiring noise up to a cache memory, malfunction due to signal delay, and unnecessary radiation. There is the present situation that total system performance is limited by the peripheral equipment.
In order to solve such a problem, it is necessary to improve electric characteristics such as crosstalk, signal delay, etc. As one of approaches to the improvement, there has been proposed a method in which LSI chips and component parts arranged two-dimensionally are mounted three-dimensionally on a substrate to shorten the length of wiring between chips to thereby achieve the improvement in electric performance and the improvement in degree of integration per unit area.
For example, such three-dimensional mounting has been proposed in JP-A-8-264712, JP-A-5-63137, etc. In those proposals, three-dimensional mounting was achieved by connecting electrodes of chips to one another through through-holes each containing an electrically conducting material buried therein by piling up semiconductor wafers. How to form the through-holes was, however, unspecified in those proposals though the through-holes were ones each having a hole size of 10 xcexcm and a plate thickness (length) of the order of hundreds of xcexcm.
Laser-processing machining or etching might be conceived for the formation of the through-holes. In the case of laser-processing, however, processing scattered matter (called dross, debris, etc.) was deposited on the neighborhood of the electrodes so that reliability was lowered. Moreover, because it was impossible to make energy per pulse large from the point of view of preventing the substrate from being damaged (breaking or cracking), a large number of pulses were required for the formation of the through-holes. Hence, a long processing time was required. On the other hand, in the case of etching, it was impossible to form a structure of a high aspect ratio because of crystal anisotropy even though an anisotropic etching technique was used.
An object of the present invention is to provide: a semiconductor chip having a vertical current conduction structure of a high aspect ratio and high reliability; a semiconductor device, a circuit substrate, and an electronic apparatus each containing such semiconductor chips; and a method for producing them.
(1) According to an aspect of the present invention, a semiconductor chip comprises: a crystalline substrate having a through-hole prepared by laser beam irradiation and anisotropic etching; an electrically insulating film formed on an inner wall of the through-hole; and a metal bump containing an electrically conducting material inserted into the through-hole, for electrically connecting one surface of the crystalline substrate to the other surface of the crystalline substrate through the electrically conducting material.
(2) According to another aspect of the present invention, the semiconductor chip of the above paragraph (1) further comprises an electrode pad formed on the one surface of the crystalline substrate through an electrically insulating film, wherein the metal bump protrudes from the one surface of the crystalline substrate while being electrically connected to the electrode pad and further protrudes from the other surface of the crystalline substrate while piercing the crystalline substrate.
(3) According to a further aspect of the present invention, in the semiconductor chip of the above paragraph (2), the metal bump is formed in the through-hole which is formed to pierce the crystalline substrate in a range of from a portion of the electrode pad on the one surface of the crystalline substrate to the other surface of the crystalline substrate.
(4) According to a further aspect of the present invention, in the semiconductor chip of the above paragraph (3), the metal bump is made of an electrically conducting material provided along the inner wall of the through-hole.
(5) A semiconductor device according to a further aspect of the present invention includes semiconductor chips described in any one of the paragraphs (1) through (4) in the condition that the semiconductor chips are laminated while the metal bumps of the semiconductor chips are connected to one another.
(6) A circuit substrate according to a further aspect of the present invention includes a semiconductor device described in the paragraph (5).
(7) An electronic apparatus according to a further aspect of the present invention includes a circuit substrate described in the above paragraph (6).
(8) A method of producing a semiconductor chip according to a further aspect of the present invention comprises the steps of: forming a prehole in a crystalline substrate by laser beam irradiation; and enlarging the prehole by anisotropic etching to thereby form a through-hole.
(9) A method of producing a semiconductor chip of the above paragraph (8), according to a further aspect of the present invention, further comprises the steps of: forming an electrically insulating film on an inner wall of the through-hole; and forming an electrically conducting material in the through-hole having the electrically insulated inner wall to thereby form a metal bump for electrically connecting one surface of the crystalline substrate to the other surface of the crystalline substrate.
(10) In a method of producing a semiconductor chip of the above paragraph (9), according to a further aspect of the present invention, the leading hole is formed by laser beam irradiation at a portion of an electrode pad portion formed on the crystalline substrate, and the electrode pad is electrically connected to the metal bump.
(11) In a method of producing a semiconductor chip of the above paragraph (9) or (10), according to a further aspect of the present invention, the crystalline substrate is a silicon substrate.
(12) In a method of producing a semiconductor chip of the above paragraph (11), according to a further aspect of the present invention, the silicon substrate is surface-oriented to a (100) face.
(13) In a method of producing a semiconductor chip of the above paragraph (11), according to a further aspect of the present invention, the silicon substrate is surface-oriented to a (110) face.
(14) In a method of producing a semiconductor chip of any one of the above paragraphs (8) through (13), according to a further aspect of the present invention, protective films are formed on one surface of the crystalline substrate and on the other surface of the crystalline substrate, respectively, so that the crystalline substrate is irradiated with a laser beam through the protective films.
(15) In a method of producing a semiconductor chip of the above paragraph (14), according to a further aspect of the present invention, the silicon substrate is irradiated with a laser beam from a surface of the crystalline substrate on which the electrode pad is formed.
(16) In a method of producing a semiconductor chip of the above paragraph (14), according to a further aspect of the present invention, the silicon substrate is irradiated with a laser beam from a surface of the crystalline substrate which is opposite to the surface on which the electrode pad is formed.
(17) In a method of producing a semiconductor chip of the above paragraph (14), according to a further aspect of the present invention, the silicon substrate is irradiated with a laser beam from a surface of the crystalline substrate on which the electrode pad is formed and from a surface of the same opposite to the surface on which the electrode pad is formed.
(18) In a method of producing a semiconductor chip of the above paragraph (14), according to a further aspect of the present invention, the electrode pad has an opening portion in its center portion and is covered with a protective film so that the laser beam is made to pass through the opening portion across the protective film.
(19) In a method of producing a semiconductor chip of the above paragraph (18), according to a further aspect of the present invention, a patterned protective film is formed between the electrode pad and a surface of the silicon substrate so that the etching form by anisotropic etching is defined by the shape of the protective film.
(20) In a method of producing a semiconductor chip of any one of the above paragraphs (8) through (19), according to a further aspect of the present invention, the substrate is irradiated with a laser beam split by a phase grating.
(21) In a method of producing a semiconductor chip of any one of the above paragraphs (8) through (19), according to a further aspect of the present invention, the substrate is irradiated with a laser beam converted into randomly polarized light.
(22) In a method of producing a semiconductor chip of any one of the above paragraphs (8) through (19), according to a further aspect of the present invention, the crystalline substrate is irradiated with a circularly polarized laser beam.
(23) In a method of producing a semiconductor device according to a further aspect of the present invention, semiconductor chips produced by a production method according to any one of the above paragraphs (8) through (22) are laminated on one another.
(24) In a method of producing a circuit substrate according to a further aspect of the present invention, a semiconductor device produced by a method for producing a semiconductor device according to the above paragraph (23) is incorporated in a circuit substrate.
(25) In a method of producing an electronic apparatus according to a further aspect of the present invention, a circuit substrate produced by a method for producing a semiconductor device according to the above paragraph (24) is mounted on the electronic apparatus.
For example, the present invention has the following advantages in accordance with the aspects thereof.
{circle around (1)} There is no limitation due to difficulty of forming a small hole relative to the thickness because a through-hole is formed by anisotropic etching after a prehole has been formed by laser beam irradiation. Hence, a through-hole of a high aspect ratio is obtained.
{circle around (2)} Although a long processing time is required when a through-hole is formed only by laser processing, a batch process can be made so that the processing time can be shortened because a prehole is enlarged by anisotropic etching to thereby form a through-hole. Moreover, the diameter of the through-hole little varies and is made uniform.
{circle around (3)} Further, the enlargement of the hole size (hole width) of the through-hole can be adjusted optionally by adjustment of the opening size of a protective film and the time of anisotropic etching.
{circle around (4)} Further, dross produced by laser beam irradiation or processing dust remained on the inner wall is removed automatically when anisotropic etching is performed.
{circle around (5)} The surface roughness of the inner wall due to laser processing or the thermal denaturation thereof due to the laser is removed by anisotropic etching so that a smooth crystal face of silicon is exposed. Hence, an electrically insulating film can be formed so securely in the electrically insulating film-forming step that any pinhole cannot be formed in the electrically insulating film. Moreover, the thickness of the electrically insulating film can be set to meet the minimum requirement.
{circle around (6)} Protective films are formed on the front and rear surfaces, respectively, of the crystalline substrate so that the crystalline substrate is irradiated with a laser beam through the protective films. The laser beam irradiation is performed from a surface on which the electrode pad is formed, from a surface opposite to the surface on which the electrode pad is formed, or from both the surfaces. Because any place to be etched can be exposed by the laser beam irradiation, the step by photolithography can be omitted so that the cost of production can be reduced. Further, dross produced by the laser beam irradiation is removed when anisotropic etching is performed. Moreover, the aforementioned protective films can serve also as films for protecting various kinds of devices formed in the semiconductor chip when anisotropic etching is performed.
{circle around (7)} The electrode pad has an opening portion in its center portion and is covered with a protective film. The laser beam passes through the opening portion of the electrode pad. Hence, the electrode pad is never cut by the laser beam, so that etching the electrode pad is avoided when anisotropic etching is performed.
{circle around (8)} A patterned protective film is formed between the electrode pad and the substrate so that the etching form of anisotropic etching is defined by the shape of the protective film. Hence, an optional etching form is obtained in accordance with the shape of the protective film, so that a through-hole having an optional shape is obtained.
{circle around (9)} Because the substrate is irradiated with a laser beam split by a phase grating, preholes can be formed in a plurality of places simultaneously. Hence, the processing time can be shortened greatly.
{circle around (10)} Because the substrate is irradiated with a laser beam which is circularly polarized, processing bending of the prehole can be suppressed. Hence, unnecessary enlargement of the hole size of the prehole can be suppressed. Further, because the processing bending of the prehole can be suppressed, the positional accuracy of the hole can be improved and the reliability thereof can be improved correspondingly. Moreover, the electrode pad can be small-sized correspondingly. When the circularly polarized laser beam is replaced by a laser beam converted into randomly polarized light, the same effect as described above can be also obtained.
{circle around (11)} Because the prehole is enlarged by anisotropic etching to thereby form a through-hole after the prehole has been formed in an electrode pad portion of the substrate having the electrode pad on its surface by laser beam irradiation, a predetermined effect (in which a semiconductor chip having a vertical current conduction structure of a high aspect ratio and high reliability can be produced efficiently) is obtained even in the case where the substrate is not crystalline.
{circle around (12)} Semiconductor chips are laminated onto one another so that a semiconductor device is produced. Hence, the method of producing the semiconductor device involves the aforementioned advantages. Moreover, because an LSI chip can be achieved three-dimensionally, the length of wiring can be shortened so that the electric performance of the LSI chip can be improved (increase in speed, reduction of unnecessary radiant waves and reduction of malfunction). At the same time, the degree of integration per unit area can be improved. Hence, various kinds of electronic apparatuses can be small-sized. Because the semiconductor device is produced by direct lamination of semiconductor chips, the laminate can be shaped not like a pyramid but like a rectangular parallelepiped. Also from this point of view, the degree of integration per unit area can be improved.